This invention relates to an apparatus for uniforming the heat of a gun barrel by shrouding a gun of, e.g., a tank with a heat-pipe type dissipation cylinder for dissipating heat locally generated because of solar radiation or as the result of shooting so as to improve shooting accuracy.
On receiving solar radiation, the temperature of the upper side of a barrel of a gun mounted on a tank and the like is sharply raised by solar heat and, on the contrary, the temperature of the lower side thereof is only slightly raised. For this reason, the difference in thermal expansion accompanied by the difference in temperature between the upper and lower sides is known to cause the front end of a gun barrel, if it is long, to slightly curve downward. Since the extent to which the barrel is curved varies with weather conditions and so on, it allows of reduction in shooting accuracy.
Moreover, the inside wall of a barrel is subjected to impacts because of gas resulting from the combustion of a propellant every time a shell is shot. The further addition of heat generated by the mechanical abrasion between the shell and the inside wall of the gun barrel raises the temperature thereof, thus affecting the life of the material used. Furthermore, the contact resistance between the shell and the barrel changes as the caliber of the gun barrel expands because of thermal expansion and also affects the initial velocity of the shell, thus decreasing shooting accuracy.
In order to improve shooting accuracy, as shown in FIG. 1, an annular heat-pipe type dissipation cylinder 4 is tightly conductively attached to the outer periphery of a gun barrel 2 projecting from a gun turret 1 so as to transfer heat quickly from a high temperature zone to a low temperature one by making use of the evaporation of hydraulic fluid in the heat pipe and latent heat resulting from condensation cycles, thereby efficiently to disperse the heat locally generated throughout the whole area of the barrel. An apparatus for uniforming the heat of a gun barrel by dissipating the heat thus generated in the manner described above has already been proposed by the present inventors (Japanese Utility Model Application No. 7867/84).
In that case, the barrel 2 is, as shown in FIG. 1, equipped with a smoke discharger 3 halfway and formed in such a manner that the outer diameter of the gun barrel is made gradually thinner from the base on the turret side toward the front end thereof. When the heat-pipe type dissipation cylinder 4 is attached to the long barrel 2, the dissipation cylinder 4 is divided into a plurality of pieces beforehand in the longitudinal direction of the gun barrel 2 and the thus divided pieces of the heat-pipe type dissipation cylinder are arranged one after another and attached to the barrel, each of the independently built pieces conforming in dimension to each barrel block in the corresponding fitting position. Through the method of individually attaching the pieces thereof, they are readily fabricated and attached thereto and, in case part of the heat pipe is bombed and damaged, the loss of the function of the heat pipe is limited to that portion and advantageously prevented from spreading over the whole heat dissipation cylinder.
FIGS. 2 and 3 show the construction of the above divided heat pipe type dissipation cylinder. Each piece of the heat-pipe type dissipation cylinder 4 obtained by dividing it into a plurality of pieces along the longitudinal direction of the barrel comprises a C-shaped inner cylinder 5 and outer cylinder 6 made of sheets mutually sealing welded, a ring flange 7 for closing both axial edge faces between the inner and outer cylinders 5, 6 and a linear flange 8 for closing the edge faces of a cut P on the periphery. These parts constitute a tightly closed cylinder of double construction which is C-shaped in cross section. A heat-pipe hydraulic fluid is supplied to the closed internal space, whereas a wick 9 is bonded to the inner walls of the inner cylinder 5 and the outer cylinder 6. A space 10 for allowing the hydraulic fluid to evaporate is formed inside the outer cylinder 6. Moreover, clamping flanges 11 face each other with the cut P between and clamping bolts 12 tighten the flanges. The actuation of heat pipe is made in the manner described above and the the heat locally generated is thermally transferred from the high temperature zone to the low temperature zone on the evaporation-condensation cycle to uniform and radiate the heat throughout the whole area of the dissipation cylinder. To attach the heat-pipe type dissipation cylinder 4 to the gun barrel 2, the axial cut P is widened to have the gun barrel covered therewith and subsequently the clamping bolts 12 are used to tighten the clamp flanges 11 at several places so that the heat dissipation cylinder may be firmly attached to the whole periphery of the gun barrel.
The gun barrel thus enclosed with the cylinder is less affected by solar heat and what is generated by shooting to a certain extent and contributes to the improvement of shooting accuracy. On the other hand, the conventional heat-pipe type dissipation cylinder limits the heat-uniforming performance and, because the periphery of the heat dissipation cylinder is most subjected to direct solar radiation, the amount of solar heat intruding into the cylinder is large. Therefore, solar heat greatly affects the heat-uniforming properties of the gun barrel on its peripheral direction and the disadvantage is that shooting accuracy is insufficiently improvable. In consequence, it has been called for to improve the apparatus for uniforming the heat of a gun barrel contributable to the improvement of shooting accuracy by minimizing the thermal effect of solar radiation thereon.